Long-term experiments carried out during the current grant period indicated that among the interventions started early in life a) dietary restriciion, and b) administration of cholestane-triol were the most potent maneuvers capable of preventing the age-related arterial changes leading to atherosclerosis in the pigeons. In contrast to their effect in older pigeons, estrogens caused an increase both in the incidence of atherosclerosis and the concentration of cholesteryl esters in the aorta. The main objective of this renewal application is to define the mechanisms responsible for the diverse changes in the aortic cholesteryl ester accumulation and incidence of atherosclerosis following early treatment with cholestane-triol and estrogens (especially in females) in the White Carneau pigeon. Studies are proposed to carry out 1) subcellular distribution of cholesterol and cholesteryl esters in the aorta, 2) endogenous cholesteryl ester synthesis and hydrolysis, 3) arterial concentration and synthesis of Squalene (measure of cholesterol synthesis), 4) relative contribution of plasma cholesterol and cholesteryl esters to arterial sterol accumulation, and 5) changes in the biosynthesis of specific prostaglandins. In addition, the effect of a few early intervention, feeding of dihomo-gamma-linolenic acid (to stimulate the synthesis of antithromobitic E1 series of Prostaglandins) on platelet aggregation and arterial changes will be carried out. These studies will provide insight into the mechanism responsible for the effect of estrogens and cholestane-triol noted on the key events of atherogenesis and also explore the significance of the prostaglandin system in atherogenesis.